1KG Precision Gcr15 Steel Ball Bearing Replacement Bearings Size: 3mm-10.5mm

Remove one ball from the existing bearing and measure its diameter with a micrometer or digital caliper. Match that measurement to the closest available size in the variant list. For inch-fraction bearings, note that 3.175mm = 1/8", 4.763mm = 3/16", 6.35mm = 1/4", 7.938mm = 5/16", and 9.525mm = 3/8". Even a 0.1mm mismatch can cause excessive play or binding, so measure before ordering.

GCr15 is a high-carbon chromium bearing steel equivalent to AISI 52100 (US) and SUJ2 (Japan). It contains approximately 1% carbon and 1.5% chromium, which allows it to be hardened to 60–66 HRC. This makes it significantly harder and more fatigue-resistant than general-purpose carbon steels, which is why it is the industry standard material for precision bearing balls in motors, gearboxes, and machine tools.

GCr15 steel provides moderate corrosion resistance through its surface finish, but it is not stainless steel. For applications exposed to water, cutting fluids, or outdoor conditions, apply a compatible bearing grease or oil to the balls and housing. For highly corrosive environments, consider stainless steel bearing balls (AISI 440C) instead. These GCr15 balls are best suited for dry or lightly lubricated indoor applications.

These are loose replacement balls intended for open bearings or assemblies where the balls are accessible for replacement. Sealed (2RS) and shielded (ZZ) bearings are typically replaced as complete units rather than by individual balls. If your bearing is open or has a removable retainer, these balls are suitable — confirm the ball count and diameter match your original specification.

The piece count per kilogram varies by diameter. As a rough guide: 3mm balls yield approximately 4,700–5,000 pieces per kg, while 10mm balls yield approximately 130–150 pieces per kg. If you need a specific piece count for a project, contact us with your diameter and required quantity and we can advise on the appropriate pack size.

GCr15 bearing balls are designed to handle both radial (perpendicular to shaft) and axial (along shaft) loads when used in the correct bearing housing. The actual load rating depends on the bearing design, housing geometry, and number of balls — not the balls alone. For specific load calculations, refer to your bearing manufacturer's engineering data using the ball diameter and bearing series as inputs. These balls are replacement-grade and meet the hardness and sphericity requirements for standard precision bearing service.